10th February 2012

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IOS: Reverse SSH Console Access – Part 2

25th June 2008 By 5 Comments

Accessing the line port using SSH only.

The advantage to this option is that you need only allow TCP 22 (SSH) through your firewall.

From a *nix platform, you use the following command line:

ssh gf:39@10.216.4.10

When using putty in interactive mode, at the username prompt just put username:number at the prompt.

Putty Profile

If you configure putty profiles (which I use to run putty from the command line).

putty ssh selecta.jpg

Connecting from the IOS prompt on your terminal server

Accessing a port on your terminal server using the IOS command line, where 40 is the line number of the serial port that you want connect to.

lontrm01#ssh -l gf:40 10.216.4.10

{Thanks to Emanuele who posted a comment on the original post}

HELP: How do you enter Break Characters to enter ROMMON ?

I have not been able to successfully enter a break character / sequence to break into the boot sequence when using Reverse SSH. From my research, it seems that the break characters when using SSH are different from those using telnet.

I am sure that there is an answer – please leave a comment if you have any tips.

List of Standard Break Keys

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About Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at EtherealMind.com and on Twitter @etherealmind and Google Plus

  • Emanuele

    Hi Greg,
    I think there is no standard key. On openssh using ~B you ask to remote server to send a BREAK to remote server. But I’m not sure SSHv2 on cisco implement this. I’ve nothing connected to the only reverse SSH box I have, so I can’t test.. :)
    And I see no telnet break-on-ip or ip-on-break for ssh.. :-/

    • http://etherealmind.com Greg Ferro

      I tried ~B on OSX Terminal but it didn’t work. I also activated the ‘telnet -on-break’ but it didn’t work either. The only way I got it to work was to remove the line from the rotary group, telnet (not SSH) as normal, connect a windows keyboard, and open a windows terminal emulator in Parallels. Which isn’t really very good.

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  • http://networknerd.wordpress.com Rob
  • http://networknerd.wordpress.com Rob

    Sorry I meant to type “ip ssh break-string” command in the previous post